The potent hydroxyl radical scavenger, 1-phenyl-3-(2-thiazolyl)-2-thiourea (PTTU) (50, 100, 150, and 200 mg/kg i.p. 1 hr. before paraquat) failed to prevent deaths in mice injected with paraquat (30, 35 and 40 mg/kg i.p.). Cellular resolution autoradiography of lungs removed at 3, 24 and 48 hrs. after intravenous injection of (methyl-3H) paraquat chloride into male C57B1/6J mice indicated that the radioactivity within the lung was confined almost entirely to the alveolar type II cells.